The Science Behind Overeating

The biological basis for hunger and obesity put forth by David S. Ludwig and Mark I. Friedman supports a more far-reaching theory of overeating.

Food as an addiction has been the mainstay of many successful eating programs. This means that far from just the biological task of reducing hunger, food is used to deal with fear, doubt and insecurity. Like all addictions, there is both biological and psychological causation that in turn leads to acute withdrawal symptoms. Food, though, is a necessity that must be handled daily.

The outbreak of morbid obesity coincides with the addictive ease of obtaining low-cost, sugary foods and the way in which the body uses these foods.

Reducing the ease of obtaining high-sugar foods fights only one part of addiction. The more long-term solution would be to acknowledge overeating as an addiction and deal with it in eating addiction programs.

KENNETH SATIR Longboat Key, Fla., May 19, 2014

The writer is a retired psychologist.

To the Editor:

David S. Ludwig and Mark I. Friedman argue that high levels of insulin trigger hunger, leading to greater food intake. However, my colleagues and I showed that even without a change in caloric intake, high levels of insulin can lead to greater body fat (American Journal of Physiology, 1985).

In a study of rats tube-fed the identical daily diet, those also receiving daily insulin injections became fatter than those receiving control saline injections. The laws of conservation of energy must still hold, of course, meaning that the additional injected insulin was able to increase the efficiency of converting calories from food into body fat.

Thus, when it comes to body weight or fat gain, a calorie does not always equal a calorie.

ALLAN GELIEBTER New York, May 19, 2014

The writer is senior research scientist, Obesity Nutrition Research Center at Mount Sinai St. Luke’s and Columbia University Medical Center.

To the Editor:

David S. Ludwig and Mark I. Friedman’s article illustrates the difficulty of producing enduring change in the complex mechanisms in obesity. Not mentioned is the fact that the paradoxical, resistant-to-change quality of fat and carbohydrate metabolism is rooted in evolutionary adaptations over millions of years.

Back then, extreme scarcity of calories was a fact of life, and a heightened taste and desire to stock up on energy-rich foods was a potentially lifesaving trait. Only recently have any populations had the caloric abundance prevalent in countries like ours.

Long-term, evolved survival strategies like this one need to be deeply built in and tied to intense emotions that are sensitive to environmental stress. The cravings may trick us now, but for millenniums they needed to be robust and hard to change.

Manipulation by family, culture and industry plays upon these natural inclinations. Medical research and treatment might be more effective and less pathologizing of patients if it recognized the profound, adaptive safeguards that underlie these broadly human cravings.

MALCOLM OWEN SLAVIN Cambridge, Mass., May 18, 2014

The writer is a co-author of “The Adaptive Design of the Human Psyche: Psychoanalysis, Evolutionary Biology and the Therapeutic Process.”

To the Editor:

Before lurching toward refined carbohydrates as the culprit for our high rates of obesity, I hope that we stop to consider that two foods with a very high glycemic index (white rice and baguettes) are staples of two countries with relatively low rates of obesity (Japan and France).

Let’s not repeat the mistakes of the past and pin the blame for health issues on nutrients not found to be problematic by both epidemiology and biology. The stakes are simply too high.

SUSAN ALLPORT Katonah, N.Y., May 18, 2014

The writer is the authorof “The Queen of Fats: Why Omega-3s Were Removed From the Western Diet and What We Can Do to Replace Them.”

To the Editor:

An important corollary of the carbohydrate-insulin-obesity hypothesis advanced by David S. Ludwig and Mark I. Friedman is that insulin should be used rarely, if at all, in Type 2 diabetes, and sparingly in Type 1 diabetes. Diet and exercise must be the mainstays of therapy.

Insulin, and many other agents, predictably cause significant weight gain in Type 2 diabetes. Since overeating and central obesity underlie the disease, these treatments make matters worse.

Obesity should be the primary target of therapy. Blood sugar control should be of secondary importance. Drugs that promote blood sugar control while worsening obesity should be avoided.

RICHARD AMERLING New York, May 18, 2014

The writer is an associate professor of clinical medicine at the Icahn School of Medicine at Mount Sinai.